The electrodes of some electric components, such as pseudo-capacitors and electrochemical double-layer capacitors, contain, as electrode material, activated carbon, metal oxides, such as ruthenium, nickel and manganese oxide, or conductive polymers, such as polythiophenes, polyanilines, or polypyrroles. This electrode material is frequently applied in powder form to current collectors with favorable electrical conductivity characteristics or produced on the current collectors via chemical or electrochemical deposition processes. The electrically conductive current collectors are frequently present in the form of thin metal foils, such as aluminum foils. In the case of aluminum foils, the aluminum oxide on the surface of the foil, which increases electric resistance, is removed by etching, for example, so that the electrically conductive intermediate layer and then the electrode material can be subsequently applied. The surface of the aluminum foil is frequently enhanced by producing a surface topography via etching, for example. This enhances the surface of the electrodes, thereby resulting in capacitors with higher capacitance.
To improve the bond between the current collector and the electrode material, an electrically conductive intermediate layer, such as graphitic carbon, is frequently applied to the current collector. To some extent, the particles of the intermediate layer can also be mixed into the electrode material.
Especially in the case of electrochemical double-layer capacitors for high-performance applications, the current collectors and the electrode materials arranged thereon are produced as thinly as possible, so that a large area of electrodes connected in parallel can be incorporated into a predetermined capacitor volume. As a result, the volume-specific bonding resistance between the current collector and the electrode layer is reduced, leading to more powerful capacitors.
As a result of stress caused by electrical operation or temperature change, the contact between the electrode coating on the electrode material and the current collector deteriorates. This leads to an increase in the serial resistance of the capacitor, and thus to higher resistive losses during the operation of these capacitors. This increase in serial resistance is caused by corrosive effects on the surface of the current collector and separation of the electrically conductive intermediate layer from the surface of the current collector.